VulnerabilityPublished 13 Nov 2026

CVE-2026-126192: Soup Sieve · General sibling combinator inside :has() matches untrusted HTML in quadratic time

Affects adr-viewerSource GCVE Database

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Authoritative record:CVE-2026-126192· Medium 6.3

Not known to be exploited · CVSS 6.3 Medium.

Data as of 13 Nov 2026, 21:17 UTC

CVSS 4.0 base score

6.3Medium

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CNA (GitHub_M)	CVSS 4.0	6.3

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: Present
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: None
Vulnerable system availability: Low
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: Present: The successful attack depends on the presence of specific deployment and execution conditions of the vulnerable system that enable the attack. These include: a race condition must be won to successfully exploit the vulnerability (the successfulness of the attack is conditioned on execution conditions that are not under full control of the attacker, or the attack may need to be launched multiple times against a single target before being successful); the attacker must inject themselves into the logical network path between the target and the resource requested by the victim (e.g. vulnerabilities requiring an on-path attacker).
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the Vulnerable System are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 12 Nov 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 13 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Homebrewadr-viewer`pkg:brew/adr-viewer`Other threats	Affected >=1.3.0	Fixed in–

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AI-suggested

This quadratic time behavior is an expected characteristic of :has() selectors with general sibling combinators and not a bug. Users should carefully design selectors to avoid applying :has() with general sibling combinators on elements with many children or untrusted input. Prefer using more restrictive combinators such as > or + inside :has() to limit traversal. Avoid overly general anchor selectors like *. If the risk is unacceptable, input containing :has() selectors can be rejected or calls to selector evaluation can be wrapped in timeouts to prevent long-running processes.

Description

CVE-2026-126192 is a performance-related vulnerability in Soup Sieve where using a general sibling combinator (~) inside the :has() CSS selector causes quadratic time complexity when matching against untrusted HTML. This can lead to significant CPU consumption and potential denial of service if an attacker controls the HTML input and the selector is applied. The issue arises because the selector implementation performs nested scans over sibling elements, causing processing time to grow quadratically with the number of siblings. The vulnerability affects Soup Sieve versions starting from 1.3.0. Mitigations include careful use of :has() selectors, avoiding large numbers of children on the anchor element, and preferring more restrictive combinators like > or + inside :has().

Impact

The impact is primarily on availability. An attacker controlling the HTML input to an application using Soup Sieve with a selector containing a general sibling combinator inside :has() can cause the selector evaluation to consume excessive CPU time, potentially stalling or degrading the application's performance. This can lead to denial of service conditions. There is no indication of confidentiality or integrity impact. The vulnerability is triggered by the combination of a developer-authored selector and attacker-controlled HTML input.

Summary

The vulnerability in Soup Sieve (CVE-2026-126192) involves the use of a general sibling combinator (~) inside the :has() pseudo-class selector, such as div:has(a ~ b). When this selector is evaluated against untrusted HTML containing many sibling elements, the matching process runs in O(n²) time due to nested scanning of siblings. This can cause the CPU time to increase dramatically with the number of siblings, potentially stalling applications that run such selectors on attacker-controlled HTML. The adjacent sibling combinator (+) does not exhibit this issue as it remains linear in complexity. The root cause is that the implementation cannot short-circuit when the right-hand sibling is absent, leading to exhaustive comparisons. This is a known performance characteristic of :has() selectors with general siblings, not a bug per se, but an area where performance improvements are possible. The vulnerability impacts Soup Sieve versions >=1.3.0. The CVSS 4.0 score is 6.3 (medium severity), reflecting the potential for availability impact through CPU exhaustion.

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Description

AI analysisMachine-generated, updated 13 Nov 2026, 21:17 UTC

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